Cupola



July 1950 v H. L. KUEHLTHA-U 2,513,569

CUPOLA I Filed Jan. 4. 1947 Y, a Sheets-Sheet 1 July 4, 1950 H. L.KUEHLTHAU CUPOLA Filed Jan. 4, 1947 3 Sheets-Sheet 2 f w m f 0 0 w m v oo o 3 w 7 y k w w 5 Mo" w H 7 H a I w a b m 2. [pl 1,. 1. u I. 2 3

y 1950 H. 1.. KUEHLTHAU 2,513,569

CUPbLA Filed Jan. 4, 1947 s Sheets-Sheet s @atenied .Fuiy 4, 19502,513,569 corona Hugo L. Kuehlthau, Chicago, 111., assignor to WhitingCorporation, Harvey, 11]., a corporation of Illinois Application January4, 1947, Serial No. 720,161

7 Claims.

The present invention relates generally to cupolas. More particularlythe invention relates to that type of cupola which serves as aninstrumentality or medium for melting metal, is supported in an elevatedposition by way of a plurality of laterally spaced legs and comprises anupstanding cylindrical shell having at the lower end thereof a dropbottom in the form of a pair of oppositely .disposed, complemental,hinged doors.

In connection with operationof a cupola of the aforementioned type ithas heretofore been the practice to utilize a vertically extending propto maintain the doors constituting the shell bottom in their closedposition. At the conclusion of a metal melting operation the prop isjerked from under the doors by the cupola operator. As soon as the prop'is jerked from its operative position the doors swing downwards and theresidual materials within the cupola fall onto the subjacent portion ofthe fioor over which the cupola is mounted. After opening of the doorsthe discharged materials are shoveled into a suitable receptacle inorder that they may be taken to a dump. The practice of utilizing anupstanding prop for holding the doors in their closed position duringoperation of the cupola is subject to certain objections. In the firstplace the cupola operator in connection with jerking of the prop fromunder the doors is likely to be injured, especially when the doors areheavy and there is a large amount of residual materials within thecupola shell. Secondly, the use of a prop precludes a receptacle frombeing placed under the cupola so as to receive or catch the residualmaterials after downward swinging of the doors.

One object of the invention is the provision. in connection with acupola of the type under consideration, of a novel latch arrangementwhich, when in its operative orlocked position, serves to hold thebottom forming doors in their closed position and, when released,permits the doors to swing downwards into their open position. Byemploying such a latch arrangement injury to the cupola operator isavoided and it is possible prior to opening or unlatchingof the doors toinsert under the cupola a receptacle for receiving the residualmaterials within the cupola directly upon opening of the doors.

Another object ofthe invention is to provide in addition to the latcharrangement remotely controlled power means for shifting the latcharrangement into and out of its operative or latched position.

A further object of the invention is the proviwhich like numerals ofreference denote corresponding parts throughout the several views:

Figure l is a fragmentary side view of a cupola embodying the invention;

Figure 2 is a horizontal section taken on the line 22 of Figure 1 andillustrating in detail the construction and arrangement of the powermeans i for shifting the latch arrangement into and out of its operativeor latched position;

Figure 3 is a fragmentary vertical section taken on the line 3-3 ofFigure 2 and showing the construction, design and arrangement of thepower means for swinging the bottom forming doors of the cupola upwardsinto their closed position;

Figure 4 is an enlarged vertical section taken at right angles to Figure3 and on the line 44 of Figure 2, and illustrating the design andconstruction of the latch arrangement for releasably holding the doorsin their closed position; and

Figure 5 is an enlarged vertical transverse section taken on the line 55of Figure 4 and showing one of the latches constituting the latcharrangement.

The cupola which is shown in the drawings constitutes the preferred formor embodiment of the invention. It is designed primarily for use in afoundry to melt metal and as its principal components comprises a shellIll, a bottom structure ll having a drop bottom [2, legs I3 forsupportin the shell in an elevated position with respect to the floor ofthe foundry or other establishment in which the cupola is disposed, alatch arrangement M for latching or retaining the drop bottom in itsoperative or closed position, power means l5 for shifting the latcharrangement into and out of its latched position and power means l6 forswinging the drop bottom into its closed position.

The cupola shell I0 is of standard or conventional construction and hasthe interior or inner periphery thereof lined with refractory material,

. erably two hinges for each of the doors.

It is cylindrical so far as contour o'r configuration is concerned andembodies at a point slight-' ly above the bottom structure M an annularwind box l1 and a circular series of equidistantly spaced tuyeres l8.The wind box is provided with a tangentially arranged nipple I9 wherebyit may be connected to receive air under pressure from a compressor orother source (not shown). The tuyeres l8 are located beneath the windbox I! and serve to introduce air under pressure from the wind box intothe interior of the shell in, order to promote combustion of thecombustible material with which the shell is charged.

The bottom structure ll of the cupola comprises in addition to the dropbottom I2, a square bottom plate 20, a pair of parallel, laterallyspaced I-beams 2| and a pair of parallel, laterally spaced angle bars 22and 23. The bottom plate 20 underlies and projects outwards from thelower end of the cupola shell l and has a central circular opening 24which is substantially the same in diameter as the shell interior. TheI-beams 2| underlie, and extend lengthwise of. two opposed marginalportions of the bottom plate 20. They ,are arranged so that the websthereof extend vertically and have the upper flanges thereof suitablyfixedly secured to the super] acent marginal portions of the bottomplate 20. The angle bars 22 and 23 extend at right angles to the I-beams2|. They correspond in length to the I-beams and embody horizontal,inwardly extending legs and vertical, outwardly disposed legs. Thehorizontal legs of the angle bars rest on, and are welded or otherwisefixedly secured to, the other two side marginal portions of the bottomplate 20 of the cupola bottom structure The ends of the angle bars areconnected to the ends of the I-beams by way of vertically extendinggusset plates 25 and vertically extending angle bars 26 in order thatthe bottom structure It is rigid. The upper marginal portions of theplates 25 are weldedor riveted to the ends of the vertical legs of theangle bars 22 and 23 and the outer side margins of the gusset plates areconnected to the ends of the webs of the I-beams by way of thevertically extending angle bars 26. The drop bottom I2 constituting apart of the cupola bottom structure U consists of a pair of oppositelydisposed, com- I plemental, semi-circular doors 21 and 28 and these areconnected to the bottom plate 20 by way of hinges 29 in order that theyare capable of swinging downwards from a closed position wherein theyare horizontal into an open position wherein they hang down under thesupporting structure I I. The doors are so arranged that when they arein their normal or closed position the chordal margins thereof are inaligned and abutting relation. As well understood in the art the dropbottom is covered with sand before the cupola is placed in operation.There are pref- Each hinge comprises a door carried hinge arm 30, a pairof angle brackets 3| and a pivot pin 32. The hinge arms 30 of the hingesare connected to the under sides of the doors and extend outwards asshown in dotted lines in Figure 2. The pairs of angle brackets 3| areconnected to, and depend from, the bottom plate 20 and are arranged instraddled relation with the outer ends of the hinge arms 30. The pivotpins 32 extend through aligned holes in the vertical parts of the anglebrackets 3| and the outer ends of the hinge arms 30.,

The legs it of the cupola are four in number and extend vertically. Thelower ends of the legs have fioor engaging feet 33 and the upper ends ofthe legs have rigid horizontal plates 34 which underlie, and are welded,riveted or otherwise fixedly secured to, the ends of the bottom flangesof the I-beams 2 I. As shown in Figure l, the legs l3 are spacedlaterally apart a suflicient distance to permit a wheel equipped opentop receptacle 35 to be moved under the cupola shell I0. It iscontemplated that after operation of the cupola the receptacle 35 willbe moved into the position shown in Figure 1 wherein it is disposedunder the cupola shell. It is also contemplated that after properpositioning of the receptacle the doors 2'! and 28 constituting the dropbottom l2 will be swung downwards into their open position to the endthat the residual materials within the cupola shell will fall directlyinto the receptacle. The top of the receptacle is at least as large asthe opening 24 in the bottom plate 20 in order that the receptacle whenproperlypositioned beneath the drop bottom will catch all of theresidual materials upon opening of the bottom.

The latch arrangement I4 serves releasably to hold the doorsconstituting the drop bottom in their operative or closed position andcomprises an I-beam 36 and a pair of latches 31. The I- beam extends atright angles to the I-beams" 2| and consists of a web 38, a topflange-39 and a bottom flange 40. One side portion of the top flange ofthe I-beam 36 underlies and is bolted to the chordal margin of the door21 and the other side portion of said top flange is adapted when thedrop bottom of the cupola is in its closed position to underlie andsupport the chordal margin of the door 28, as best shown in Figures 3and 5. The ends of the I-beam 36 terminate inwards of the I-beams 2|(see Figure 4) and are provided with a pair of studs 4|. The latterextend lengthwise of the I-beam 36 and have the inner end portionsthereof disposed within cutouts 42 in the ends of the web 38 of theI-beam 36. The cutout defining portions of the web are welded to theinner ends of the studs in order that the studs are held in fixed orrigid relation with the I-beam 35. The outer ends of the studs arecylindrical and when the two doors are in their closed position aredisposed directly inwards of the central portions of the webs of theI-beams 2|. The latches 31 are mounted on the inner ends of a pair oflaterally spaced coaxial stub shafts 43. They embody arcuate seats 44for the outer ends of the studs 4| and are adapted after the doors 2'!and 28 are swung upwards into their closed position, to be swung into aposition wherein they underlie said outer ends of the studs and thushold the doors in their closed position. Reverse swinging or rotation ofthe latches disengages them from the outer ends of the studs and freesthe doors so that they drop downwards into their open position. Thearcuate seats are so designed and arranged that when the latches areswung into their latched position while the doors are but partiallyclosed they will cam the doors upwards into fully closed position. Thestub shafts 43 are rotatably mounted in bearings 45 which fit withincollars 46. As shown in Figure 4 the collars extend through alignedholes in the central portions of the webs of the I-beams 2|. The holedefining portions of said webs are welded to the central portions of thecollars 46 in order that the collars are held in fixed or rigid relationwith the I- beams 2|. The stub shafts 43 are connected together forconjoint rotation by way of a rock shaft 48, a pair of arms 49, a pairof links 59 and a pair of arms 5|. The rock shaft 48 extendshorizontally and is located beneath and outwards of the angle bar 22 ofthe bottom structure II. It extends in parallel relation with said anglebar and has its ends journalled in a pair of bearings 52. As best shownin Figure 2, such bearings are mounted on certain of the gusset plates25. The arms 49 are fixedly connected to, and project downwards from,the ends of the rock shaft 48. The arms 5| are connected to, and projectdownwards from, the outer ends of the stub shafts 43 and are arranged inparallel relation with the arms 49. The links 50 extend horizontally andhave certain of the ends thereof pivotally connected to the outer endsof the arms 49. The other ends of the links are pivotally connected tothe outer or distal ends of the arms 5 I. When the rock shaft 48 isrocked in a counterclockwise direction as viewed in Figure 1 itoperates, through the medium of the arms 49, the links 59, the arms SIand the stub shafts 43, conjointly to swing the latches 31 out of theirlatched position wherein, as previously pointed out, they underlie theouter ends of the studs 4|. Reverse rocking of the rock shaft operatesto swing the latches into their latched position. It is contemplatedthat after the bottom forming doors 21 and 28 are swung upwards intotheir operative or closed position the rock shaft will be rocked so asto cause the latches to swing into latched relation with the studs 4|.At the conclusion of operation of the cupola, the rock shaft is rockedso as to disengage the latches from the studs. As soon as the latchesare swung out of engagement with the studs the doors, in response to theaction of gravity, swing downwards.

The power means l5 for shifting the latch arrangement l4 into and out ofits latched position comprises a cylinder-piston device 53 and this ispositioned over one of the I-beams 2| and consists of a cylinder 54 anda piston 55. The cylinder 53 is provided on the central portion thereofwith a pair of aligned outwardly extending trunnions 56 and is pivotallysupported by way of a U-shaped bracket 51 which, as shown in Figures 1and 2, is mounted on the bottom plate 20 of the bottom structure 2|. Thetrunnions 56 fit rotatably within bearing forming holes in the sides ofthe bracket 51 and permit the cylinder to tilt in a vertical plane. Thepiston 55 is slidably mounted in the cylinder 54 and is provided with arod 58 which extends slidably through a packing gland at one end of thecylinder and has its outer end pivotally connected to the upper end ofan upwardly extending arm 59. The lower end of such arm is fixedlyconnected to the rock shaft 48. When the piston is slid in one directionit operates, through the medium of the piston rod 58 and the arm 59, torock the rock shaft 48 in one direction. Opposite sliding movement ofthe piston results in rocking of the rock shaft in the oppositedirection. As heretofore pointed out rocking of the rock shaft in onedirection eflects swinging of the latches 31 into their operative orlatched position and reverse rocking of the rock shaft operates to swingthe latches into their unlatched position with respect to the studs 4|on the outer ends of the I-beam 36. The cylinderpiston device 53 iscontrolled by, and forms a part of a fluid pressure system comprising asupply pipe 60 and a 2-way valve 6|. The supply pipe 69 lsconnected toan air compressor or any other suitable source (not shown) of air underpressure. The 2-way valve 6| is located any suitable distance from thecupola and consists of a casing 62 and a rotatable plug 63. The casinghas a top port 64, a pair of side ports 65 and 66, and a bottom port 61.The discharge end of the air supply pipe 6ll is connected to the topport 6|. The side port 65 is connected to one end of the cylinder 54 ofthe cylinder-piston device 53 by a flexible pipe 66 and the side port 66is connected to the other end of the cylinder by a flexible pipe 69. Thebottom port 61 is open to atmosphere and serves as a venting medium. Theplug 63 of the 2-way valve 6| embodies a pair of diametrically oppositearcuate ducts 10. Each of these ducts extends through an arc of and isadapted to bridge and establish communication between two adjoiningports in the valve casing 62. When the plug is positioned as shown inFigure 1 one of the ducts 10 effects communication between the ports 64and 66 and the other duct effects communication between the ports 65 and61. This arrangement of the plug results in air under pressure flowingfrom the air supply pipe 60 into one end of the cylinder 54 via the port64, the one duct 10 and the pipe 69 and also results in venting of theother end of the cylinder by way of the pipe 68, the port 65, the otherduct 19. and the. port 61. The air under pressure entering the one endof the cylinder causes sliding movement of the piston 55 in onedirection. When the plug 63 of the valve 6| is turned throughout an arcof 90 from the position shown in Figure 1 one of the ducts 19 bridgesand establishes communication between the ports 64 and 65 and the otherduct 10 establishes communication between the ports 66 and 61. Inconnection with such positioning of the plug air under pressure isdelivered from the air supply pipe 60 into the other end of the cylindervia the port 64, the one duct 10, the port 65 and the pipe 68 and theone end of the cylinder is vented by way of the pipe 69, the port 66,the other duct 18 and the port 61. Upon entry of air under pressure intosaid other end of the cylinder the piston is caused to slide in theopposite direction. As heretofore pointed out sliding movement of thepiston in one direction results in swinging of the latches 31 into theirlatched position and sliding movement of the piston in the oppositedirection results in swinging of the latches into their unlatchedposition wherein they free the bottom forming doors 21 and 28 so thatthey swing downwards into their open position.

The power means l6 for swinging the doors constituting the drop bottom|2 upwards into their closed position is in the form of a winchcomprising a rotatable drum 1|, a gear unit 12 for turning the drum, anda cable 13. The drum and gear unit are positioned in side by siderelation adjacent the central portion of the angle bar 23. The drumextends around and is fixedly secured to a horizontally extending shaft14, the ends of which are journalled in bearings 15. The latter areconnected by way of brackets 16 to a vertically extending plate 11 whichis welded or otherwise fixedly secured to the central portion of thevertical flange of the angle bar 23. The gear unit 12 comprises a worm18 and a worm wheel 19 and these are disposed in a gear box 80. The wormwheel surrounds, and is keyed to one end of, the shaft 14 and is in meshwith, and adapted to be driven by, the worm 18. The latter is mounted ona horizontally extending shaft 8| which is journalled in suitablehearings in the gear box. One end of the shaft projects outwards of thegear box and is provided with a chain wheel 7 22. An endless chain 83 istrained around the chain wheel 82. When the chain is pulled in onedirection it operates through the medium of the chain wheel 82, theshaft 8|, the worm 12 and the worm wheel 19 to turn the drum II in onedirection. Reverse pulling of the chain results in reverse turning ofthedrum. One end of the cable 13 is anchored to, and wound around, thedrum and the other end of the cable is provided with a hook 84. When itis desired to use the power means It to swing the bottom forming doors21 and 28 upwards into their operative or closed position the hook 84 ishooked onto the central portion of the vertical leg of the angle bar 22.When the hook is so hooked the central portion of the cable underliesthe doors 21 and 2|. bar 22 the drum is turned so as to draw up on thecable. As the cable is drawn up or wound around the drum it operates toswing the doors upwards. Upward thrust resulting from drawing up of thecable is transmitted to the door 21 by a sheave N and is transmitted tothe door 21 by way 01' a sheave 86.

The sheave 85 extends vertically, is mounted rotatably on an inverted U-shaped bracket 81, the intermediate part of which fits against, and isconnected to, the central portion of the bottom flange 4|! of the I-beam36. The sheave 86 extends vertically and is mounted rotatably on one endof an elongated bracket 08. The other end of the bracket 88 is connectedto the chordal margin of the door 28. The bracket 88 is of such lengththat when the two doors 21 and 28 are in their closed position thesheave 86 is disposed at a lower level than the sheave 85. As a resultof this the door 28, in connection with a door closing operation, closesslightly ahead of the door 21. As shown in Figure 3, the cehtral portionof the cable 13 is trained around the sheaves 85 and 86.

After use of the cupola the wheel equipped receptacle 35 is wheeled intoplace under the drop bottom l2. Thereafter the valve 62 is manipulatedso as to cause air under pressure to enter the right hand end of thecylinder 54 as viewed in Figure 1. This results in the piston beingshifted to the left and operating through the medium of the piston rod58, the arm 59, the rock shaft 48. the arms 49, the links 50, the armsBI and the stub shafts 43 to swing the latches 31 into their unlatchedposition. As soon as the latches are swung into such position the doors21 and 28 are released and drop downwards by gravity. In connection withdownward swinging of the doors the residual materials in the cupolashell fall into the receptacle 35. When it is desired to close thebottom forming doors the hook 84 on the outer end of the cable 13 ishooked onto the central portion of the angle bar 22 and the centralportion of the cable is trained around the sheaves 85 and 86. After thehook is hooked in place the drum 1| of the winch is turned so as to windup the cable. In connection with winding up of the cable the doors arecaused to swing upwards into their closed position. As soon as the doorsreach such position the valve 62 is shifted into its other position inorder so to control the cylinder-piston device that the latter operatesto swing the latches into their latched position wherein, as previouslypointed out, they underlie the studs 4| on the end of the I-beam 36.After the latches are in place the hook 84 is unhooked from the anglebar 22.

The herein described cupola may be manipulated with facility so far asopening and clos- Aiter hooking of the hook onto the angle it includesthe latch arrangement I4, the power means it for shifting the latcharrangement into and out of its latched position, and the power means I!for swinging the doors into their closed position.

The invention is not to be understood as restricted to the details setforth since these may be modified within the scope of the appendedclaims without departing from the spirit and scope of the invention.

Having thus described the invention what I claim as new and desire tosecure by Letters Patentis:

1. In a cupola of the type that comprises an elevated shell adapted foruse in melting material therein and provided with a horizontalframe-like bottom structure including a bottom hinged to swingupwards'and downwards into and out of a closed position wherein itextends across the lower end of the shell, and a structural elementunderlying and extending across the bottom and rigidly connected to thelatter, the combination of a latch arrangement adapted releasably tohold the bottom in its closed position and embodying a pair of studsconnected fixedly to, and projecting outwards from, the ends of thestructural element and a pair of latches associated with the studs,respectively, and mounted on the bottom structure so that when thebottom is in its closed position they are capable of being swung about ahorizontal axis into and out of a latched position wherein they underliesaid studs, and means mounted on the bottom structure and including ahorizontal rock shaft for connecting the latches for conjoint swingingmovement.-

2. In a cupola of the type that comprises an elevated shell adapted foruse in melting material therein and provided with a horizontalframe-like bottom structure including a bottom hinged to swing upwardsand downwards into and out of a closed position wherein it extendsacross the lower end of the shell, and a structural element underlyingand extending across the bottom and rigidly connected thereto, a latcharrangement adapted releasably to hold the bottom in its closed positionand embodying a pair of studs connected fixedly to and projectingoutwards from, the ends of the structural element and a pair of latchesassociated with the studs, respectively, and mounted on the bottomstructure so that when the bottom is in its closed position they arecapable of being swung about a horizontal axis into and out of a latchedposition wherein they underlie said studs, means mounted on the bottomstructure and including a horizontal rock shaft for connecting thelatches for conjoint swinging movement, and power means mounted on saidbottom structure and arranged and adapted to effect rocking of the rockshaft in either direction.

3. In a cupola of the type that comprises an elevated shell adapted foruse in melting material therein and provided with a horizontal frame--like bottom structure including a bottom hinged projecting outwardsfrom, the ends of the structural element and a pair of latchesassociated with the studs, respectively, and mounted on the bottomstructure so that when the bottom is in its closed position they arecapable of being swun'g about a horizontal axis into and out of alatched position wherein they underlie said studs, means mounted on thebottom structure and including a horizontal rock shaft for connectingthe latches for conjoint swinging movement, and fluid pressure meansadapted and arranged to effect rocking of the rock shaft in eitherdirection and including a cylinder-piston device mounted on the bottomstructure and operatively connected to said rock shaft.

4. In a cupola of the type that comprises an elevated cylindrical shelladapted for use in melting material and provided with a frame-likebottom structure including a drop bottom in the form of a pair ofoppositely disposed, complemental, semi-circular doors hinged to swingupwards and downwards into and out of a closed position wherein theyextend across the lower end of the shell, and an elongated structuralelement underlying and extending across the chordal margin of one of thedoors, connected rigidly thereto and adapted to underlie and support thechordal margin of the other door when the two doors are in their closedposition, the combination of a latch arrangement adapted releasably tohold the bottom in its closed position and embodying a pair of studsconnected fixedly to, and projecting outwards from, the ends of thestructural element and a pair of latches associated with the studs,respectively, and mounted on the bottom structure so that when thebottom is in its closed position they are capable of being swung about ahorizontal axis into and out of a latched position wherein they underliesaid studs, and means on said bottom structure for connecting thelatches together for conjoint swinging movement.

5. In a cupola of the type that comprises an elevated cylindrical shelladapted for use in melting material and provided with a frame-likebottom structure including a drop bottom in the form of a pair ofoppositely disposed, complemental, semi-circular doors hinged to swingupwards and downwards into and out of a closed position wherein theyextend across the lower end of the shell, and an elongated structuralelement underlying and extending across the chordal margin of one of thedoors, connected rigidly thereto and adapted to underlie and support thechordal margin of the other door when the two doors are in their closedposition, the combination of a latch arrangement adapted releasably tohold the bottom in its closed position and embodying a pair of studsconnected fixedly to, and projecting outwards from, the ends of thestructural element and a pair of latches associated with the studs,respectively, and mounted on the bottom structure so that when thebottom is in its closed position they are capable of being swung about ahorizontal axis into and out of a latched position wherein they underliesaid studs, and means mounted on the bottom structure and including ahorizontal rock shaft for connecting the latches for conjoint swingingmovement.

6. In a cupola of the type that comprises an elevated cylindrical shelladapted for use in melting material and provided with a frame-likebottom structure including a drop bottom in the form of a pair 01'oppositely disposed, complemental, semi-circular doors hinged to swingupwards and downwards into and out of a closed position wherein theyextend across the lower end of the shell, and an elongated structuralelement underlying and extending across the chordal margin of one of thedoors, connected rigidly thereto and adapted to underlie and support thechordal margin of the other door when the two doors are in their closedposition, the combination of a latch arrangement adapted releasably tohold the bottom in its closed position and embodying a pair of studsconnected fixedly t0, and projecting outwards from, the ends of thestructural element and a pair of latches associated with the studs,respectively, and mounted on the bottom structure so that 'when thebottom is in its closed position they are capable of being swung about ahorizontal axis into and out of a latched position wherein they underliesaid studs, means mounted on the bottom structure and including ahorizontal rock shaft for connecting the latches for conjoint swingingmovement, and power means mounted on said bottom structure and arrangedand adapted to effect rocking of the rock shaft in either direction.

7. In a cupola of the type that comprises an elevated cylindrical shelladapted for use in melting material and provided with a frame-likebottom structure including a drop bottom in the form of a pair ofoppositely disposed, complemental, semi-circular doors hinged to swingupwards and downwards into and out of a closed position wherein theyextend across the lower end of the shell, and an elongated structuralelement underlying and extending across the chordal margin of one of thedoors, connected rigidly thereto and adapted to underlie and support thechordal margin of the other door when the two doors are in their closedposition, the combination of a latch arrangement adapted releasably tohold the bottom in its closed position and embodying a pair of studsconnected fixedly to, and projecting outwards from, the ends of thestructural element and a pair of latches associated with the studs,respectively, and mounted on the bottom structure so that when thebottom is in its closed position they are capable of being swung about ahorizontal axis into and out of a latched position wherein they underliesaid studs. means mounted on the bottom structure and including ahorizontal rock shaft for connecting the latches for conjoint swingingmovement, and fluid pressure means adapted and arranged to effectrocking of the rock shaft in either direction and including acylinder-piston device mounted on the bottom structure and operativelyconnected to said rock shalt.

HUGO L. KUEHL'I'HAU.

REFERENCES CITED The following references are of record in the file oi!this patent:

UNITED STATES PATENTS Number Name Date 45,030 Ellis Nov. 15, 18641,286,632 Hodge Dec. 3, 1918 1,448,480 Bedell Mar. 13, 1923 1,563,949-Baker Dec. 1, 1925 1,883,501 Black et a1 Oct. 18, 1932 2,102,823 WalshDec. 21, 1! 2,196,789 Dean Apr. 9, 1010 2,429,285 Woolley Oct. 21, 1M!

